about the use of plasma arc in the industry
Among various schemes proposed for processing and metals using arc plasma, the most promising are those that use plasma torches direct action (the anode is a molten metal bath). Almost unlimited possibilities of increasing power and high efficiency of the direct action of plasma torches caused the appearance of the real possibility of their wide industrial use for melting and refining of high quality metals [1]. Schematic diagram of the melting metal in a plasma-arc furnace with a refractory lining is shown in Fig. As well. The shape of the bath and the materials used for lining of the hearth and working space, plasma-arc furnace is no different from an ordinary electric arc furnace.
Water-cooled copper anode is mounted flush with the bottoms and are in contact with molten metal. Non-consumable cathode of the plasma torch is made of a thick tungsten rods, clamped in a copper current-carrying collet. Water-cooled copper nozzle of the plasma torch at the same time serves to ignite the arc, its formation and cathode protection against splashes of metal and slag. Pre-evacuated furnace chamber zaspolnyaetsya arising from the plasma torch gas (argon, nitrogen, hydrogen), and after reaching a certain pressure, usually close to atmospheric pressure, the melting process begins. Initially, the plasma arc in the charge proplavlyaet narrow well, and the liquid metal, flowing down, accumulates on the bottoms, and then melted the entire volume of the bath. Degassing and refining of metals with particular intensity occur on the surface of the bath where the liquid, superheated plasma jet more metal is in contact with neutral or reducing gas atmosphere furnace. For the mixing of the liquid metal in the furnace bottoms has two solenoid connected in series to the power circuit of the plasma torch. The magnetic field produced by these coils, interacting with the magnetic field current flowing through the bath causes the liquid metal in motion. Plasma torches are used for melting the DC to several thousand amperes. Arc voltage as a function of the composition, gas flow, and its length varies in the range 30-150 V. Often, to increase the capacity of the furnace for melting metal in a bath are several torches simultaneously. The efficiency of plasma torches in the cladding is 85%. Electricity consumption for melting is almost the same as in the conventional electric arc furnaces. Now we study the furnace running on AC plasma torches. Plasma melting in comparison with other methods of fusion has the advantage of metal contamination is eliminated undesirable impurities such as carbon from the graphite electrodes used in conventional arc furnaces, the plasma jet may consist of any desired mixture of gases, which allows the furnace to maintain any atmosphere - oxidation, replacement or neutral, in a plasma-arc furnaces can achieve high and easily regulated temperature, and process stability simplifies the problem of its regulation. Great prospects for obtaining high purity metals reveals developed at the Institute of Electric them. Paton method of plasma-arc remelting (PDP). Scheme of RAP is shown in Fig., B [2]. The rod of the feed material, the so-called boom, the shape of the cross section of which can be any, is fed at a constant speed and melted one or more of the torch plasma arc, which is the anode surface of the bath of molten metal in a water-cooled copper mold. Flowing down from the rod of uniform droplets of metal heated plasma jet and spreads over the surface of the bath. In contact with a controlled atmosphere chamber gas is refined metal and hardens under the influence of cold walls of the mold is pulled out of it with a certain constant speed in a continuous billet round or rectangular cross section. Including all the advantages of the process described earlier, this process provides a more stable and high quality metal remelted without mixing it. With the ability to more accurately re gulirovaniya temperature molten metal by changing the geometrical and electrical parameters of the plasma arc process of PDP is more flexible than existing processes, vacuum arc and electroslag remelting. For example, the PDP can be changed within certain limits the temperature of overheating of the metal bath, regardless of the speed of melting rods and pulling of the ingot, which is very important for process control of metal refining (removal of gas, deoxidation of the metal, removing the impurities of low-melting non-ferrous metals). In addition, uniform heating bath provides a flat bottom configuration of the molten metal bath that provides a high quality of the crystallizing ingot, ie, provides the density, uniformity, directed crystallization of its vertical axis. With the use of a closed system of recycling and regeneration of the working gas powerful set of plasma melting and remelting can compete with electric furnaces.
See also:
Plasma Welding
Plasma Welding Introduction
Plasma Welding Technique
Microplasma Welding
Gases for plasma processing of materials
Separation of plasma jet cutting
Compression of the arc
The energy properties of the plasma arc
Rationalization of plasma welding
Plasma welding and spraying
The plasma melting and remelting
Plasmatron. Requirements for plasmatron
Plasmatron. Schemes, classification
Classification by type of electrode plasma torches
Classification of torches by the nature of the current
Structure of the plasmatron basic units
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